Processor cache does not detect changes in cccid

[doug-walker]

The Processor cache in the Config object tries to be smart and detect which context variables changed which might invalidate cached results. Unfortunately it currently misses changes to the cccid setting of a FileTransform (which is allowed to be a context variable).

An example is in the unit tests from PR #1696, see OCIOArchiveTest.py line 284.

The work-around is to use setProcessorCacheFlags to turn off the caching.